Introduction: Effectiveness of radiation therapy can be improved through increased accuracy in radiotherapy calculations. The proposed research will focus on two types of cancer, prostate and lung. The proposed prostate cancer research is an extension of earlier work while the lung cancer research is a new area of interest. Background: Treatment for prostate cancer is successful in most cases. Although 1 in 8 men will be diagnosed with prostate cancer, only 1 in 34 will die from prostate cancer (American Cancer Society). Research proposed in Specific Aims 1 and 2 focuses on decreasing adverse radiation side-effects by increasing the understanding of dose distributions and side effects from Intensity Modulated Radiation therapy (IMRT) for prostate cancer. The goal of this project is to provide Radiation Oncologists the necessary information to select the most appropriate beam energy for individual patients. Lung cancer is the leading cause of cancer death in the United States, approximately 6 out of 10 people with lung cancer die within 1 year of being diagnosed (American Cancer Society). Improving the therapeutic gains in lung cancer is imperative. Specific Aims 3 and 4 focus on improving the accuracy of dose calculations in lung cancer radiation therapy with the long term goal of understanding how much radiation dose is necessary to increase cure rates. Hypothesis: Increased accuracy in radiotherapy dose calculations can reduce adverse side effects from prostate cancer radiotherapy and can increase the therapeutic gain for lung cancer radiotherapy. Specific Aims: The following research aims will be addressed: (1) Perform skin dose measurements to evaluate skin reactions for prostate cancer patients treated with 6MV beam energy for IMRT;(2) Perform Monte Carlo calculations (in phantom) of dose to peripheral organs from IMRT, expandable to individual patient calculations;three years of protected time to facilitate her transition to an established cancer researcher. Her research plan is based on her previous work in improving the quantification of dosage effects for intensity-modulated radiotherapy (IMRT).